Railway traffic controlling apparatus



April 6, 1943- H. A. WALLACE RAILWAY TRAFFIC CONTROLLING APPARATUS Filed Sept; 17, 1941 8 Sheets-Sheet l "ria INVENTOR I" Allhlld0l H15 ATTORNEY' &

He! BY ww NM llllllvL April 6, 1943. H. A. WALLACE RAILWAY TRAFFIC CONTROLLING APPARATUS "s Sheets-Sheet 2 A MR , @Ria M TSN Filed Sept. 17, 1941 w mum IE: 1 h

Q w \ww QWN mw \5 QN v 5km 1 NW. I NNM ANN$ Mb NQM T m .agqn

HJS' ATTORNEY April 6, 1943. H. A. WALLACE RAILWAY'TRAFFIC CONTROLLING APPARATUS Fiied Sept. 17, 1941 s Sheets-Sheet, s

llll l INVENTOR Herber H18 ATi'OENEY April 6, 1943. W L CE 2,315,887

RAILWAY TRAFFIC. CONTROLLING APPARATUS Filed Sept. 17 '1941 s Sheets-Sheet? INVENTOR E'Pbe .Zl/allacv.

Ms ATTORNEY 8 Sheets-Sheet 5 H. A. WALLACE RAILWAY TRAFFIC CONTROLLING APPARATUS Filed Sept. 1'7, 1941 k--- ----i-- ---o k Em INVENTOFQ April 6, 1943.

April 6, 1943.

H. A. WALLAQE RAILWAY TRAFFIC CONTROLLING APPARATUS Filed Sept. 1'7, 1941 ENVENTOR P I I E T m 3943- H. A. WALLACE RAILWAY TRAFFIC CONTROLLING APPARATUS Filed Sept. 17, 1941 8 Sheets-Sheet '7 1 l I I I l l l l I l l I l l I I l l l I l l l l l I I l l l ll Q If It m

@WNNNN m max? WQNN mi- 1-1-11-1, 1- IWN MIli--- L INVENTOR erber .Zl/allaee.

"H15" ATTORNEY April 6, 3943.

H. A. WALLACE RAI LWAY TRAFFIC CONTROLLING APPARATUS 8 Sheets-Sheet 8 Filed Sept. 17, 1941 I la Fq z . INVENTOR .[flallaoa H15 A'i'ToRNEY Patented Apr. 6, 1943 RAILWAY TRAFFIC CONTROLLING V i APPARATUS Herbert A. Wallace, Ea ewood, Pa; as'si'gma The Union Switcli'la Signal Company, Swissvale, Pa a corporation of-Pennsylvania Application September 11, 194-1, serial Isa-411,162

'2' Claims.

My invention relates to railway traflic controlling apparatus, and it has particular reference to the organization of such apparatus into railway block signal systems for governing tr'afiic movements in both directions over stretchesof single track railway. More particularly, my invention relates to systems of the class wherein the direction of traffic movements is governed from a central office by means of a suitable communication system, and in which the signals are controlled in accordance with trackway conditions without the use of line wires.

An object of my invention is to providerailway signal systems of the class described and incorporating novel and improved means for controlling signals through the medium of coded or periodically interrupted current supplied to th track rails.

Another object is to provide railway signal systems of the class described and incorporating novel and improved means whereby signals governing traftic in both directions on a stretch of single track railway are controlled by trafiic conditions on the track by means of current transmitted wholly through the track rails of the stretch.

A further object of my invention'is to provide novel and improved railway signal systems for governing traffic in both directions on a stretch of single track railway wherein the direction of traflic is controlled by means selectively controlled from a central omce station and the signals are controlled by means of -current transmitted through the track rails, thereby obviating the'necessity of line wires along the track for controlling the signals.

An additional object is to provide novel and improved signal systems of the class described.

The above-mentioned and other important objects and characteristic features of my invention which will become readily apparent from the following description, are attained in accordance with my invention by controlling signalsgoverm ing traffic in both directions on a stretch: of railway track by providing each track section with two track circuits, one for each direction oi traffic and each comprising a track relay con-V stantiy connected and a source of current intermittently connected to the rails ofthepsection. The two track circuits of each section-are arranged to be independent of each otherdue to the characteristics of energy utilized' rand the rack circuit apparatus for eachdirection, is arranged toestabli'sh control over signalsgoverning trafic in the associated direction wholly (o1. ale-c). v

through "the medium of the trackcircuit-current. My invention-:further comprises means selectively controlled from aremote oflice or central; station and effective to control rthe rcharacteristics or' coding of the jcurrent-a'pplied to thetrack rails whereby; to :estabhshcontrol ot/erthe signals governin'gtrafiic on the stretch.

The invention further residesin the arranger ment and organizationoi railway-traffic controlling apparatus into improved forms of-block signal systems aswill be made clear inthefollowinad sc p n- 11.. .i.; 21;"

I, sh ldesc ibej wo form o a pa us emb yi y ent a d -.shal then ei i 9111; the novel features thereof in claims.

in the accompanyingdrawinss Figs. 1: 1C and 1D when placed end to end with-Fig. lA on the IBft COIIStitRtB a diagrammaticview showing one form-of apparatus embodying my invention, and will be referred to in the description as Fig. 1.- Figs. 2A, 2 13,20 andZD, when placed end to end with Fig. 2A on the 1ef t,'c0n stitute another diagrammatic View, -Which will be referred to as Fig. 2,;representing a modified eme m d in mri i n Pith an: at r r e in: i s: l t-. 52; i e il'i firl In each pf the two views, similar reference characters have been employed, to'designate corresponding parts. A 7

Referring to-Figl, the referencecharacters Land In designate the tra ck railsfofla stretch of a a tra k- X qnnest d at nd by means of'a track switch Wl to asidingfor passing track -Y and connected at the opposite end by another switch W2 to another siding-or passing track Z. The rails ofstretch X are divided-by insulated joints 2 into a plurality 1 of successive adjoining track sections J K,-'*K L, LM and I I he reference characters s with" distinguishing prefixes designatesignals for governing traffic on stretch X Eastbound trafiic, that is, trafiic operating from left to right asviewed' in -Fig. 1, is governed by signal JSIor- 2S and by signal- 5S, while trafiicin .the opposite} or; westbound direcon i g e s nal i o al ss d wer *In addi o si ls13$ae fiiare prov d d o r n t r n e tr fiintgthe dase tion iandMr ..respsptive rl i n ls-m he.ot-anylde ed' n ut.;.. p o fi s de int n;z t is s l sm at thesisn lsare of h s ar hlisht pe .rha i inaan operatin .;m c -,hani mlsuc as is showni United states Letters:.. 3a en N ranted Lockhart for Light signals. It is deemed sufiicient to state that when the mechanism of a signal S is energized by current of one polarity, it is conditioned to display its clear indication; when ene gized by current of the opposite polarity, the signal is conditioned to display its approach indication; and when the mechanism is deenergized the signal is conditioned to display its stop indication. Each signal also is provided with an associated circuit controller comprising a movable member 4 which is operated by the associated signal mechanism to its upper or front position when the signal is conditioned to display either its clear or its caution aspect, and which member is operated by the signal mechanism out of its front and into its back position when the signal is conditioned to display its stop aspect. Each signal also has a signal lamp, designated by the reference character SL, which lamp normally is dark but which at times becomes illuminated in a manner to be made clear presently. As shown, the signals 38 and 68 preferably compris two searchlig ht-signal units mounted on a single mast. I shall refer to these units as being upper and lower units, corresponding to their location on the mast, and have designated the upper and lower units by the reference characters of the sig nal together with the suffix I or 2 respectively.

It is, of course, to be understood that the specific arrangement of signals shown in the drawings is merely illustrative and other arrangements of signals may be employed. For example, additional signals may be provided for the stretch in pairs, as at location corresponding to L, or singly if desired.

Each section of track isprovided with two track circuits, one for each direction of traffic, both including the rails of the section and arranged to be independent of each other due to the distinctive characteristics of the energy employed. Section KL, for example, has two track circuits formed by connecting suitable sources of differently characterized currents to opposite ends respectively of the section, and by connecting two track relays, designated by the reference characters TR with suitably distinguishing prefixes, to the track rails at opposite-ends of the-section, respectively. The track relays of the sections are arranged to re spond only to current of the character supplied at the opposite end of the section, and for the purposes of this description I shall assum that the distinctively characterized currents employed are alternating currents of different frequencies, and that the relays are conditioned by suitable tuning means, to respond selectively toalternating current of one frequency or the other.

As shown in Fig. 1, th track circuit apparatus of the several sections is arranged-in such manner that the rails of each section normally are supplied at the-east-bound entrance or left-hand end, as viewed-in the drawings, with current'of a particular frequency tocontrol a track relay-TR at the other end arranged'to respond only to current of such particular frequency, and are'supplied at the westbound entrance or right-hand end with current'of-a different frequency which controls another track relay TR'at the left-hand end arranged to respond only to current of such different frequency. Considering section K-L, for example, the rails of-this-section aresupp'lied at end K with alternating current of a particular frequency by means of a track transformer 4T1 which has-'itssecondary winding Sconnected to the rails and has itsprimary winding :fi-con- (iii nected through a circuit to be traced shortly, to

a transformer LTI which in turn is connected'to a pair of line wires 1 and 8 supplied with energy from a suitable source of alternating current, such as a generator, not shown, generating current of the particular frequency. Such current may, for example, have a frequency corresponding to that ordinarily employed in railway signaling to control train-carried apparatus such as cab signals. Current of this frequency I shall term current of the first or train-control frequency, and for the purposes of this explanation I shall assume that this frequency is of the order of cycles per second. At the opposite end L of the section, relay 5TR is connected through a receiving transformer 5RT and a rectifier RX to the rails of the section, and the connection of the relay to the rails is suitably tuned by means which may, for example, include a condenser 9, to eifec tive resonance at the frequency corresponding to the frequency of current applied at the opposite end of the section. At times, however, another condenser is utilized to tun relay 5TB, andcondenser 9 or I0-is rendered effective to tune the connectionof relay 5TB to effective resonance at the "first or at another frequency according as contact ll operated by a relay 58R, hereinafter referred to, is in its released back position or is in its attracted front position, respectively.

The rails of section K-L are supplied at end L with current of the other frequency through track transformer .5TT having a secondary winding 5 connected tothe traclcrails and its primary winding6 connected through a circuit presently to be traced, to a source of alternating current having a frequency different from the first frequency. Current of such different frequency may be obtained from any suitable source such as, for example, another pair of line wires connected to another generator generating current of such differentfrequency, or as shown, such current may be obtained from the secondary winding M of a transformer FT forming a. part of a frequency changer PC, which frequency changer comprises a rectifier 16 having its input terminals connected through line transformer LTZ to the line wires 1 and 8 and having its output terminals connected to the primary winding 15 of transformer FT. It is readily apparent that rectifier Hi When energized by current of the first frequency supplies two pulses of unidirectional current to winding l5 of transformer FT in each cycle of alternating current, hence there is inducedzin secondary Winding l4 bythese double frequency pulses of unidirectional current, an alternating 1electromotivieforce having a frequency which is .double the frequency of current in wires 1 and 8. It follows, therefore, that secondary winding M of transformer FT may be considered as :a source of alternating current having a second frequency of .200 cycles per second, or a frequency distinctively different from the alternating current of the first freguencysupplied at theopposite end of the secion.

Relay dTR isconnected to'the rails of section K-L at end K through rectifier RX and transformer 4RT tuned by condenser II) to effective resonance at a frequency corresponding to the second'frequency supplied atthe opposite end of the section. Another condenser 9 also is provided, and relay 4TH may be tuned to respond to current of the second or the first frequency according ascondenser ID or dis rendered effective'to tunethe circuit connection when contact I! of a relay lRPSR,..to be; referred to later, is

in its released back position'or is in its attracted front position, respectively.-

The current of each character supplied to the sections is coded or periodically interrupted in any suitable manner. The currents supplied to section KL, for example, are coded by code transmitters or coders 3CT and 4CT. These coders may be of any suitable type, and each has been represented conventionally in the drawings as comprising a constantly energized winding operating a plurality of contacts Zll, andlfill, each at a different code rate of, say, 20, '75 and 180 times per minutarespectively. -I t"is to be understood that the contacts of these transmitters close at the rate of -20,-'75 and 180 times per minute, respectively, in such manner as to produce interrupted current having on and 013? periods in the track circuit. -The currents supplied to the other sections are similarly coded either by means of code. transmitters CT, or by means'of the track relays TR which may be em ployed in the usual manner to repeat the code from one section into the next; 7

The track relays TR. areof the code following type, and each has associatedtherewith code responsive or decoding apparatus arranged to respond'to frequency type code energy. This decoding apparatus comprises a decoding transformer, designated by'the reference character DT with a suitably distinguishing prefix, a plurality of code responsive relays, designated by the reference characters FSA, BSA, Hand D, each with a distinguishing prefix, and a decoding unit DUiSfi. The decoding apparatus represented in Fig. 13 associated with relay 3TB, is typical and a detailed description of such apparatus will serve also to describe the decoding apparatus associated with each of the other track relays.

Referring now to Fig. 1B, decoding transformer EDT associated with relay 3TB has a portion of its primary winding [8 supplied with unidirectional current from a suitable source, such as a battery not shownbut having its opposite terminals designated in the drawing by the reference characters B and C, at suchtimes as contact 2} of relay 3'IR, is in its front position' to complete, a circuit extending from ter minal B through front contact 2| ,of relayBTR, the winding of relay 3FSA, and a portion of winding l8 to terminal C. When contact 2| of relay 3TB is in its back position and front contact 25 of relay 3FSA is closed, another portion of winding i8 is energized over a circuit extending from terminal B through back contact 2! of relay 3TB, front contact 26 of relay SFSA, the winding of relay 3133A, and a portion of winding: 18' to terminal C. The relays 3FSA and 3BSA are sufiiciently slow releasing as to bridge respec-' tively the off and on intervals of 20 code energy, hence when relay 3TB. operates in response to energy coded at the rate of 20 or more cycles per minute, relay til-F-SA is energized each time relay 3TB closes its front contact 2| due to an on interval of codejenergy received from the rails of the associated section and' with rent contact 2%: of relay 3FSA closed, relay 3BSA is energized each time relay 3TB closes its back contact in response to an off interval of code the associated section, When, however, relay 3TB is steadily energized, relay 3138A is released since its energizing circuit is held open at back contact 2! of relay 3TB, or if relay 3TB is steadily released, both relays tFSA and 3133A are released since the circuit of relay-31 8A is open at front ciated relay 3TB operates in response to coded energy received from its associated section; and that by properly proportioning the release periods of relays 3FSA and 3BSA, relay-3138A may be employed to detect operation-of its associated track relay by energy coded at the rateof' 20 or more'codecyclesper minute.

With winding 18 of transformer BDI' supplied with energy in the manner described, it is readily apparent that the direction of flux in the transformer is reversed at a rate corresponding to the rate at which relay tTRoperates its contact 2i, hence there 'is induced in secondary winding [90f transformer SDT, an alternating electromotive force having a frequency corresponding to the code rate of operation of relay 3TB. Relay 3H is'connected through a' rectifier 22 to winding l9, and the relay and transformer are proportioned and constructed in such manner that relay 31-1 is effectively energized and picked up whenever relay 3TB, operates at any one of the usual code rates 'of or more cycles per minute, but not when relay 3TB opcrates at a relatively low code rateof, say, 20 cycles per minute. 1 a

, Relay 3D is connected by means of a decoding unit DUI8E3 to winding 18 of transformer EDT. The. details of construction of decoding unit DUI are not shown in the drawings, but usually such unit comprises a reactor condenser tuning unit tuned to resonance at a frequency corresponding to the code rate. Relay 3D is, therefore, effectively energized when and only when relayi3TR operates at the 180 code rate to induce in transformer 3DT an alternatingelectromotive force having a frequency corresponding'to the 180 code rate.

Located adjacent the left-hand end, as viewed inthedrawings; of the stretch are two manua1- ly controllable switch control relays IRWSR and 'INWSR' for controllingthe adjacent switch WI, and two manually controllable signal control relays; one'relay' IRHSR, for governing the associated signals IS and ZS and the other relay ILHSR forgoverning'signal 3S. Relay lRHSR is provided-with a repeater relay IRPSR' having quiclc'p'ick-up and slow'release characteristics. Theseswitch and signal control relays as shown areremotely controlled by' means of a communication system which may be of any suitable type, but ishere assumed to be of the selective or code type, in which communication is established intermittently by means of impulse codes transmitted from an ofiice over line wires to thevarious 'field stations, as shown, for example, in the Lewis Patent-No. 2,229,249, granted on January 21, 1941; for Remote control systems.

The opposite end of the stretch is likewise provided *With two manually controllable switch control-relays 2RWSR and ZNWSR for controlling the adjacent switch W2, and two manually controllable signal" control relays, one relay.

ZRHSR' for' governing'the associated signal 5S anda'th'e 'otherrelay-IZLHSR for governing signals' TS' audits; 'These relaysas shown are controlled over the same communication system which controls the-manually controlled switch and signal control relays at the left-hand end of the stretch. Relay ZRHSR is provided with aquick pick -up, slow release repeater relay ZRPSR.

SMZ, respectively. These switch mechanisms may be of any-suitable typesuch as of, the, elec, tric;.or electropneumatic type, and, it is deemed suflicientto state that when the associatednsection J-TK is unoccupied so that relay BBSA, is

23, the selection of relay IRWSR for operation.

by the communication system causes. relay INWSR to be released, and relay IRV/TSR to. be picked-up to close its front contact 25 and cause switch mechanism SM'I to operate switch =W-I' I to its reverse position. The operationof switch W2 is similarly controlled by relay (BSA in responseto trafiic conditions in section jM-.-N' andby switch control relays 'ZNW SR and, ZRWSR- Each switch mechanism is provided in the usual manner with a circuit controller including contacts operated in accordance with the position of the switch. Contacts 21, 2-8 andz29, for example, are operated by switch. WI and switch mechanism SMI into engagement with contacts 30, 3| and 32, respectively, when switch WI is in its normal position, and are operated out of engagement with such contacts and into. engagement with contacts 33,34 and 35, respectively, when the switch is in its reverse position.

Contacts 21, 28 and 29 associated with switch mechanism SM2 are operated in a similar manner in accordance with the position of switch Thesignals SI and S2 at the left-hand end of the stretch are controlled jointly'by trafiicconditions on the stretch and by manually controllable relay I-RHSR. Whenswitch WI is in its normal position and contact 28 controlled thereby engages contact 3-l to close a circuit controlling contact 283I, the selection of relay IRHSR by the communication system for operation and consequent energization of such relay to close its front contact 37 causes signal IS to be energized over an easily traced circuit by current of one relative polarity when both relays 2D and 2H are pickedup, and to be energizedby current-0f the opposite relative polarity when relay 2D is released but relay 2H is picked up. The polarity of current supplied to signal IS when both relays 2D'and 2H are picked up is selected tolconditi on that signal to display its clear aspect, while-current of the oppositepolarity conditions the-signal to display its caution aspect. When both relays 2D and 2H are released, or relay IRHSR is'deenergized, or contact 23-3I of switch WI is opened, the signal mechanism of signal I S is deenergized and the signal accordingly is conditioned to display its stop indication. It is, of

course, readily apparent that when switch WI isv reversed so that contact 28 isoperated to close contact flit-.343, the energization of. relay IrRI-ISR causes the signal mechanism of signal ZS-to condition the signal to display its clear or its caution aspect, respectively, according as both lrelays 2D and-2H arepicked up, or relayg2D is released and relay H1 is picked up. Signal :28 obviouslyisdeenergized and isconditioned to display its stop aspect wheneverswitch WI isin its normal position so that contact 28-34 is open,

games?" TheswitchesjWI and W2 are. proyided..-with power. operated switch mechanisms SMzI and,

or whenever relay RHSR1-is released. .01: wh n both relays 2H and ZD-arereleased. Thezsignals Is and BSattheopposite: endof; the stretch are similarly: controlled by relay- ZLHSR. ,the position ofjswitchWLhand relaysaH- and 9D, as is readily apparent from an inspection of the drawing.

Signal 35 is controlled by traffic conditions in adyance and by relay ILHSR, with the upper or lowerunit respectively being selected for control according as switch WI is in its normal or its reverse position to, close contact: 2 9.. 32 or 29:35, respectively. When relay ILHSR is selected for operation --hy the communication system, and-the upper unit isselected 'by the position of switch WI for control, theunit is conditioned todisplay its clear or its caution aspect, respectively, accordingas-hoth relays ,3D and 3H are, picked up, or relay3D is releasedand relay 3H is pickedup. This unit of signal 3S of course is deenergized and is conditioned to display its stop aspect Whenever. relay. ILHSR is released, or when --both relays 3D and 3H are released. The lower unit of signal 38 is controlled over ,an obvious circuit completed-when frontcontact 39,0f relay I LHSR, switch contact, 29,.,3 5 andfront contact of re lay3BSA are closed, Signal is at the opposite end .of ;the section .iscontrolled in a similar man,- ner; ascanbeseen from ,an inspection of the drawing, by relay ZRHSR, the position of switch W2, and relays 8H, 8D and BBSA.

Signals ASand 58 are controlled in the .usual manner by the, decoding relays associated with track relays STRand fi'I'R respcctively. That is to: say, each signal. is ,conditioned to display its clear aspect when both the associated decoding relays Dand- Hare, picked up; the signal is conditioned to display its caution indication when the associated decoding relay H is picked up and the associated decoding relay Dis released; and the signal -is,conditioned to display. its stop aspect when both the associatedH and D decoding relays are released.

Th apparatus at intermediate si nal location L includes two directional stick relays 53R and BSRassociatgd with trackrelays SIR and 6TB,

respectively. Relay 53R isprQvided with a Sl w releasing repeater relay SSPS. The functions of these relays ,will'be made clear prese tly, but at thistim itshquldbepointed outt at lays 53R and 58.28 may at times be utilized to alter the tuningof track relays 5' IR and 6'ITR,respectively. Other stick relays ISRand 83R associated with track relays ITR and,8' IR, respectively, are pro- 4 vided for altering at times the tuningof' relays I'I R, and .I'ITR, respectively, while the tuningof the remaining track relays may be altered by relays IRHSR, IRPSR, ZRPSR and ,ZRHSR, as will be madeclear presently.

.In the drawings, certain contacts have been represented remote iromthe relays controlling suchcontacts,butineachcasesuch a contacthas been designated not only by a reference character individual .to such .contact but, also by placing adjacent ,thflcontact. the reference, character, of the relay operating such contact.

The apparatus embodying my invention is in its normal condition, asrepresented in the.draw ing, when switch control relays INWSR and ZNWSRare .pickedup, switches .W I andW2 are in their respective normal positions, sections .I--K, K-.-L, and M.N are unoccupied, and the sections (not shown) extending to the left ofsection J .';K and 'to :the right of section M N are likewise unoccupied. In this condition of the apparatus, signals 4S and 58 are caused to display their respective caution aspects, while signals IS, 28, 38, 6S, IS and 88 are caused to display their respective stop aspects. All track relays connected at the right-hand ends of the sections (the relays having odd-numbered prefixes) are tuned to respond to current having the first frequency while the remaining track relays connected at the opposite ends of the sections are tuned to respond to current of the second frequency. s

Coded current having the first frequency is supplied to the track rails of section JK at end J over acircuit extending from one terminal of line transformer LTI through condenser '9, back contact 96 of relay IRHSR, front contact 5| of relay lI-I, front contact 52 (when closed) of track relay ITR, primary winding 6 of track transformer 2TT and through a common connection, indicated by the reference character CC, to the opposite terminal of the secondary winding of transformer LTl. This current is caused to be coded in response to relay ITR following coded current in the rail of the section-to the left of section J-K, which section-may be supplied with track circuit current ofthe first frequency by means of apparatus substantially corresponding to that hereinafter to be described whereby the rails of the sectionextending to the right of section MN are supplied with track circuit current of the first frequency. As will be made clear presently, current of the first frequency supplied tothe section to the left of section J-K is normally; coded at the '75 code rate, with the result that relay l-TR operatesatthe 75 code rate to hold relays llZ-L- lFSA and- IBSA energized and to repeat the'75 code current into section J K. The current of the first frequency coded at the '75 code rate and supplied at J to section JK, causes relay STR to operate and to hold relays 3H, EFSA and 3BSA energized, but relay 3D is released.

, With signal SS in its stop position to cause its associated contact 4 to assume its backposition, current of the first frequency coded at the '75 code rate is likewise supplied to section KL at end K over a circuit extending from one terminal of secondary winding of transformer LT! through condenser 8, back contact 53- of relay IRPSR, front contact 55 of relay 3BSA,- contact of coder SCT, back contact 4 of signal 38, primary winding 6 oftrack transformer 4I T, and common connection CC to the other terminal of v the secondary winding of transformer LTi. It should, however, be noted that if signal 38 is conditioned to display either itscaution or its clear aspect so that the associated contact member 4 is in its front position, then the current supplied over the just traced circuit is coded at the 1.80 code rate. With, however, section K-L supplied with '75 code current of the first frequency, relay ETR operates to hold relays 5H, EBSA and EFSA energized, therebyconditioning the signal mechanism of signal 4S to cause that signal to display its caution aspect. Current of the first frequency and codedat the rate of 180 cycles per minute is supplied to the rails of section L-M at L over a circuit including the secondary winding of line transformer LTZ, condenser 9, back contact 56 of relay ESPS, contact ISEa operated hy coder ACT, front contact 4 operated by signal 15S, and-primary winding 5 of track transformer BTI; Relay ITR accordingly operates at 'the 130 code rate to hold rela-ys II-I, IFSA and lBSA picked up, and to repeatthis 180 code cur-' rent of the first frequency into section MN at M over a circuit substantially corresponding. to the circuit previously traced and over which section JK is supplied with current of the first frequency. Relay QTR of section MN of course follows this 180 code current in section MN to hold relays 9D, 9H, QFSA and QBSA picked up, but with relay 2LHSR released, signal 1S is at stop and contact 4 operated thereby is closed in its back position sothat '75 code current of the first frequency is supplied to the section to the right of section MN over a circuit substantially corresponding to the circuit previously traced and by means of which current of the first frequency is supplied at K to the rails of section K.L.

Relay liiTR normally operates at the '75 code rate due to current received from the rails of the section to the right of section MN, which rails preferably are energized by current of the second frequency coded at the code rate and supplied to the rail by, apparatus (not shown) substantially corresponding :to the? apparatus hereinafter described whereby the rails of the section extending to the left of section .JK are suppplied with current of the second frequency.

Coded current of the second frequencyis supplied to the rails of section MN .at N over a circuit extending from oneterminal of winding [4 of frequency-changer FC throughicondenser to, back contact 60 of relay. 2RHSR, front'contact 6! of relay [8H, front contact 62 (when closed) of relay IUTR,-primary winding 6' of track transformer 9'IT and the commonlconnection to the other terminal ofw-inding ['43 With relay IdTR responding to 75 code current from the rails of the section to the right of section MN, the current supplied to section M.-N is coded at the 75 code rateand causes relay BTR to respond and pick up relaysBFSA, SBSA and 8H, but relay &D is released. Relay ZRHSR also is released hence signal SS is causes to display its stopaspectv I i r I .7

With signal 6S at stop so thatitsassociated contact member 4 is in its back position, section Ll\/[ is supplied at M with 7 5 code current of the second frequency over a circuit extending from one terminal of windingM of frequency changer FC 7 through condenser l 0,'back: contact 63 ofrelayBSR, back contact 64 of relay. ZLHSR, front contact 65 of relay-8138A, co'ntact1..151of coder 5CT, back contact 4 operated by'signalfis, and the primary winding of track transformer TIT through common connection CC to the other terminal of winding M. Relay iiTRiaccordingly operates at the '75 code rate and relays 6H, .EFSA and BBSAare energized, but relay BDis released, so that signal 5S is conditioned'to display its caution aspect and contact Loperat'ed thereby'is in its front position. Current of the second fr equency coded at the 189' code-rate is sup plied at L to section K L over acircuit including secondary winding IA of frequency changer FC, condenser lfl, back contact 65 of relay ESR, contact i8il ofcoder GCT, front contact 4 operatedby signal 56 and primary winding 6 of trariktrarisformer BTT. Relay 4TB. operates at this code rate to hold relays iH, 4ESAand 4333A picked up, and to repeat this 180 code: current of the second frequency into section J-K at K over a circuit substantially corresponding to the circuit previouslytraced over which section MN is supplied v at N with current ofthe "second f r' e quency. Relay 2TH, of course follows this 180 code current to hold relays 2D, 2H,:2FS A' and 2138A. picked up, but w'ith-relay lRHSR released,

signals is and :8 controlled thereby-are conditione'd t'odisplay theirst'op aspects and contact 4 'oper'ate'd'by signal lSis operated to its back position so that 75 code current-of the secondfrequency is supplied to'th'esection to the left of section JK over a circuit including winding l4 of frequency'changer F0, condenser l0,b'ack contact-5U of 'reIay'IRHSR, back contact I20 of relay SR, contact 21- 3 0' operated by switch WI, back contact I24 of relay lLHSR,-front contact 54 of relay ZBSA, contact 15' of coder 'ICT, backco'ntact tor signal I S and theprimary winding'of-transformer ITT.

The systemsho'wn'in Fig. 1 is arranged to control -both 'wayside signals and train=carried cab signals or train controlapparatus, hence the organization is'su'ch that whenever the apparatus is conditioned for a trafii'c' movement in either direction, track circuit current 'of the first or train-'control frequency (here assumed to'be of the frequency of 100 cyciesfper second) is'fed to the rails of each section so as to be transmitted through the rails toward the approaching train, "and cu'rrent of the other frequency is'fed to the rails soas' to-be transmitted'away from the train.

In the-normal-condition of this apparatusasrepresented in the drawings, eachof the sections is supplied at its left-hand end with track circuit current-having a frequency of 100 cycles per second,-while"currentofthe other frequency of 200 cyclesper-second is fed'to the sections at the right h'and end; lhe apparatus is, therefore,

normally conditioned fora westbound train movement since-the current of train-controlfrequency is su'ppl-ied to the stretchi-n the direction to-be fed toward :a wlesflooundtrain.

I-sh'all now assume that-=the=operator wishes to "fn'ove awestbound train over-the signaled stretch.

To do's'o, apparatus-(not shown) is first conditioneuso as to "cau'sathe currentin the-section to the right "of section operating relay IOTR, to be shifted to the 20 code rate, in a manner substantially corresponding to that hereinafter described in" detail whereby relay I'LHSR is caused to shift thecode rate ofenergy supplied at J to the section to the left of section J-K. Relay H releases and completes an-o'bvious circuit path,- inclu'din'g its own back contact '61- and con- "tact 20a of coder "SGT, whereupon section M N is s'up'pliedat N'with -20code-current. Relay 8TR follows't-hfs 20code current to release "relays 8H andBlE).

The westbound signal-1S may nowbe cleared by 'theoperatorsuitablycontrolling the communication systemto cause relay iLHSRto pick up and close its frontcontact 38-to;therebyestablish the previously mentioned-circuit over which signal IS isconditio'ned to display its-clear aspect. The

lamp of signal IS is not illuminatedat this time,

however, since-the section to the rightof section M N is :assumed' to be unoccupiedarid relay IUBSA accordingly is energized to hold open its back contact 10 which whenelosed completes an obvious energizing-circuit'for the lamps SL of signals TS and 8S. Signal-1S when conditioned to display its clear aspect causesthe associated contact I to operatefrom its back to its front position to alter the coding of the current supplied at-N to the section to the right of section MN from '75 to the ij80 code rate, while front Contact of relay 'IIQJI-ISRL closes to shift the 200 cyclecurrent supplied to section from the "75 coderate to the-20code rate. This 20 code current is supplied-to section L-M over a circuit including winding T4 of frequency changer FC,

"ESE closes its front contact 12.

fastens? cuitextending from terminal B through back contact "H of relay 6H, front contact '13 of relay 5H, the winding of relay GSR. to terminal C, and relay Signal 53 when conditioned to display its stop aspect causes the associated'contact '4 to operate to its back position to complete an obvious path, including back "contact-4 of signal5S, back contact l2l -of'relay "ESR'and contact 20a, of coder 4CT, whereupon the coding ofthecurrent supplied to'section K--L- is shifted from the 180 to the 20 code rate. Relay ITR operates at this 20 code rate with the result that the-associated decoding relay 41-1 is released to'close its backcontact'fil and complete an obvious circuit path includingthat contact and contact 20a of coder 3CT, whereby section J-K is supplied with 20 code current which causes relay -2 -TR to operate at the 20 code rate so thatrelays 2H and 2D associated-therewith release. lows, therefore, that the energizationof signal control "reIay-ZLHSR clears westbound signal IS,

and conditions the opposing signal 53 to display its stop indication. Also, the apparatus controlling the opposing signals -lS and 2S -is conditioned so that if relay |-RHSR is pickedup by the communication systemin an attempt to clear signal is or 28, such signal is retained conditioned to display its stop aspect andcannot be cleared because theassociated-controlrelays 2H andJDare released.

'The operator may, however, establish control over westbound signal 3S by causing the'communication system to pick up relay ILHSR to cause it to close its front center-ch39. Signal 38 accordingly is conditioned to display its caution aspect since it has been assumed that relay'3TR normally follows 75 code in section J K, hence relaySDis normally released. However, with signal-3S conditioned to display its caution aspect, contact'4 associated therewith is caused to operate to its front position to shift the coding of current-supplied to section KL from the -'75 to the 1-80 code rate, thereby causing relay'STR to operate at the 180 code rate and energize all the associated-decoding relays SBSA, JFSA, 5H and -5D-and cause signal 38 to be conditioned to displayits clear aspect. -38 and 4S-are-not. at this time illuminated since theirobvious energizing circuits are open at back contacts of relays lBSA and GBSA, respec- The lamps SL of signals tively. I

Inaddition, the energization of relay ILHSR causes the current supplied at J to the section to the left of secti0n-JK, to be. shifted from the -code rate to the 20 code rate. This shifting of the code rate is effected when relay ILHSR opens its back contact I24 interposed in the previously traced circuit over which energyis supplied'to the section, and front contact of relay-ILHSR closes to complete an obvious circuit comprising winding M of frequency changer FC,

front contact I25 of relay -|LHSR, contact 20a of coder lCT,'back contact operated by signal |S,;and the primary windingof transformer I'I'T.

If, with the apparatus in the condition described and arranged for a westboundmovement, a'westboundtrain enters the section to'the right of'section M-N, relay ,ISTR is shunted, and relay lEiBSA releases to close its back contactv 1D to complete an obvious circuit for the lamps SL of signals is and 8S. The lamps of these signals are, therefore, approach lighted when a train enters the section in the rear of. such signals.

When the train enters section M-.-N, both relays BTR, and 9TH. arev shunted-with theresult that relays QFSA. QBSA; 9H a'nd19D release to cause signal is to display its stop aspect, and relay 8135A also releases. If the train is equipped with train-carried apparatus, which may, for ex ample, be of the type shown inEIUnitedl States Letters Patent No. 1,773,515, granted on August 19, 1930, to C. C. Buchanan for Railway traffic controlling apparatus, such apparatus of course responds to current of theLtrairr-control frequency coded at the 180 code rate available in section MN, thereby causing the train-carried cab signal to display a clear aspect.

Relays ETR and :TR areoficourse .shunted when the train enters section LM, and relay EBSA is caused to release to closeit's back contact l8 and thereby illuminate the signal lamp of signal AS. .'I'he=train-carried cab sign'alof course continues to display itsclear aspect due to the 180 code currentlof the train control frequency available in section L-M. a

When the train vacates the section to the right of section MN, current of the train-control frequency coded at the 20 code rate is supplied at N to the section to the right of section MN, relay HlTR follows 20 code current of the second frequency made available in the section in a manner to be made clear presently, and relay lllBSA picks up to open its back contact mandthereby deenergize signal-lamps SL of signals IS and 88. Current of the 20 code rate is supplied at this time to section M-N at N, but is shuntedaway from relay GTR until the train vacates the section. When this happens,- relay BTR-operates and relays SFSA and QBSA are picked up. 'Relay STR at this time also operates at the 2O code-rate, due to current supplied at M to section M-N over a circuit path comprising contact 28a of coder ECT and. back contact I25 of relay 1H. Relays SFSA and SBSA are picked up, but relays 9H and 9D remain released to maintain signal IS conditionedto display its stopaspect. The current supplied at N to the section to the right of section M-N is shifted from the 20 code rate to the 75 code rate, since front contact 54 of relay EBSA closes to complete the normal circuit, previously traced, over which 75 code current'of the train-control frequency is supplied at N to the rails of the section to the right of section M-N.

When the train accepts signal 4S and enters section KL, relays 4TH and ETR are shunted, relay 4BSA releases to complete an obvious circuit for lamp SL of signal (is, and relaysEFSA, SBSA, 5H and 5D release to condition signal is to display its stop aspect. Relay BSR is now held. energized over its stick circuit including back contact is of relay 5H, and its own front contact 22 and winding. Current of the second frequency, coded at the 20 code rate, is supplied at M to section LM, with the result that after the train vacates section L-M, relay GTR responds and picks up relays SFSA and GBSAto restore signal ES to its normally dark condition. 'Also, with signal 48 at stop so that contact 4 associated therewith is in its back position,-and' with stick relay ESR energized to close itsfront contact 80, current of the first frequency coded at the '75 code rate is supplied at L to section1L+Movera .turn condition signal is to display its caution circuit including the secondary winding of line transformer LTZyback contact 56 of relay ESPS, contact 15a of coder ACT, front contact 88, of relay BSR, back contact 4 associated with signal 45, and the primary winding of track transformer iiT'I'. This '75 code current causes operation of relay 'ITR; relays TH and TBSA are picked up; and the code current is repeated by relay 'lTR into :section M'N and causesv relay STR to pick up relays QFSA, SBSA and 9H, which relays in indication. Contact 4 associated with signal TS accordingly is caused to operate to its front position so that current or" the first or train-control frequency supplied to the section to the right of section M-'N is carried through'contact I of coderv SCT and is caused to be coded at the code rate.

--Wl1en the train accepts signal 38 and enters section J-K, both relay ZTR and 3'IR become shunted, relays '3FSA, 3338A, 3H and 3D are released to condition signal 3S to display its stop aspecuand relay ZBSA releases. Relay I'I'R is shunted, and relays iH, iFSA and IBSA release when the train enters the section to the left of section J-K. Current ofv the second frequency,

coded at the 20 coderate, is supplied at this time at L to section KL, so that when the train vacates the section, relay 4TR operates to pick up relay dBSA, thereby deenergizing the signal lamps SL of signal 38. Relay ETR also operates at the :20 code rate, due to 20 code current supplied at K to section K-L over a circuit path including back contact 54 of relay SBSA and contact 2%] of coder SCT, with the result that relay 5BSA is picked up.

1 After the train vacates section J-K, relay ZTR operates at the 20 code rate and picks up relay ZBSA, while current of the first frequency coded atthe 20 code rate is supplied at J to section J-K,.over. an obvious circuit path including backcontact iii of relay IH and contact 23a of coder ICT. Relay STR follows this 20 code current, and relay BBSA is picked up to close its-front-contact M and complete the previously traced normal circuit over which '75 code current issupplied at K to section KL. Relay 5TB follows this 75 code current to pick up relay 5H and condition signal 48 to display its caution indication. Contact 4 of signal is accordingly operates to its front position to shift the current, supplied at L to section L1V[, from the '75 to the 180 code rate. Relay 'lTR functions to repeat thisv 180 code into section M-N and cause relay 9TB to pick up relay 81), thereby causing signal lSzto be conditioned to display it proceed indication. 4

vSignal SS is conditioned to display its caution aspect, and signal 48 is conditioned to display its clear aspect, after current of the first frequency, cooled. at the '75 code rate, is made available in the section to the left of section 'J-K by apparatusnot shown but substantially corresponding to the apparatus hereinbefore described and by means of which current of the first frequency is supplied at N to the section to the right of section 'I-N. This '75 code current causes operation of relay lTR, causes relays Il-I, IFSA and lBS-A to be picked up, and causes relay. ITR to repeat the 75 code current into section J-K where it causes operation of relay 3TB. Relay 3H=.is' picked up when relay 3TB. follows 75 code, and signal SS is conditioned todisplay its caution aspect and" operates its contact 4 to its .front position'to shift the 'current, suppliedat .K to section .K-L, from the 75 to the 180 code rate. Relay TH, inrespon'ding to this 180 :code' energy, picks up relay :.5D and conditions signal 58' to display its .clearindication.

At this time, the rails of the section to the left of section J-K are supplied at J with code :current of the second frequency, and it follows that the apparatus of Fig. 1 is restored to .the condition hereinbefore described wherein it is arranged for a westbound train movement.

From the foregoing, it is readily apparent that the apparatus of Fig. 1 is organized so that when the communication system is suitably controlled by the operator topermit westbound train movements, the movement of a westbound train through the stretch causes the westbound signals in its rear to become successively cleared as the train proceeds through the stretch. This control'of the signals by the trainis established without the use of line wires solely through the medium of track circuit current transmitted through the track rails, and it permits other westbound trains to follow the first through the stretch under signal indications governed by traflic conditions in advance.

.The apparatus of Fig. 1 may now be restored to its normal condition by the operator causing the communication system to deenergize relay ZLHSR, in which case front contact 38 opens tocondition signal 18 to display its stop aspect, and back contact .64 closes to complete the previously mentioned circuit over which 75 code current is supplied at M to section L-M. This '75 code current of course causes relay BTR to operate and pick up relay :6H, thereby releasing stick relay 58R, and signal 58 is conditioned to display its caution aspect and operates its contact 4 to its front position so that v180 code current is supplied at L to section KL to cause relay 4TR to operate and pick up relay 4H. Relay '4TR is effective to repeat the 180 code current into section JK, and relay ZTR operates at this 180 code current to hold relays ZF'SA, ZBSA, Zl-I-and 2D energized, thereby conditioning the apparatus to be effective to clear si nals IS or 28 in the event that relay I RHSR is caused to be energized by the operator over the communication system.

Signal 38 may likewise be caused to display its normal stop aspect by the operator causing the communication system to release relay lL-HSR. When this happens, back contact I24 of relay lLI-ISR closes to complete the previously traced normal circuit over which '75 code current of the second frequency is supplied at J to section JK. In addition, front contact 39 of relay ILHSR opens to deenergize signal 3Sl, whereupon the associated contact 4 is caused to operate to its back position to shift the coding of current supplied :at K tosection JK to the 75 code rate, and relay 5TB. follows the 75 code current to cause relay 5D to release. Signal @S accordingly is conditioned to display its caution aspect, and the apparatus of Fig. 1 is restored to its normal condition as represented in Fig. 1.

If, with the apparatus of Fig. 1 in its normal condition, the operator wishes to move an eastbound train through the stretch, 20 code current of the second frequency is caused to be supplied to the section to the left of section JK, in a manner substantially corresponding to that hereinafter described in detail whereby 20 code current of the second frequency is supplied at N to the rails of the section to the right of section M,-N' when relay .ZRHSR is caused to be picked up. This 20 code current in the section to the left of section JK is ineffective to operate relay l-TR since'that relay is tuned to respond to current of the first frequency, hence relay lTR becomes inactive and relay IFSA, IBSA and lI-I release. Relay I SR becomes energized over an obvious pick-up circuit including back contact II of relay IH, front contact 13 of relay 2H and the winding of relay ISR, and relay lSR picks up to close its frontcontact 72 to complete an obvious stick circuit through back contact 'H of relay iH.

Relay l SR closes its front contact 92 to tune relay I'IR to current of the second frequency, whereupon relay ITR responds to the 20 code current .of second frequency and causes relays IFS-A and IBSA to pick up. In addition, contact I20 of relaylSR operates from its back to its front contact to shift the current, supplied at J to thesection to the left of section JK, from the second to the first frequency, by completing a circuit comprising the secondary winding of transformer LTI, front contact I26 of relay ISR, 2 switch controlled contact-213ll, back contact I24 of relay ILHSR, front contact 54 of relay ZBSA,

contact 15 of coder ICT, back contact l operated by signal IS, and the primary winding of trans former ITT. The operator may now suitably control the communication system-to cause relay lRI-ISR to pick up. In such an event, front contact 37 of relay IRHSR closes to complete the previously mentioned circuit of signal IS so that signal IS is cleared, and contact 4 associated therewith is operated to its front position to shift the coding of current supplied at J to the section to the left of section JK, from the '75 to the 180 code rate. Also, front contacts 82 and 83 of relay IRHSR close to shift the tuning of relays ZTR and 3TR, respectively. Relay 3TB is now tuned to respond only to current of the second frequency, while relay ZTR is tuned to respond only to current of the first or train-control frequency. Relay IRPSR picks up to close its front contact I! and tunerelay 4TR to current of the first frequency.

The energization of relay IRHSR also operates its contact 96 from its back to its front position to shift the current supplied at J to section JK from the first to the second frequency, contact 8 is operated by relay IRHSR from its back to its front position to shift the current supplied at K to section JK from the second to the first frequency, back contact 85 of relay [RHSR opens, and from contact 8! of relay IRPSR closes to complete a circuit including winding M of frequency changer F'C, condenser [9, front contact 81 of relay IRPSR, contact 2!] of coder 301', back contact 4 operated by signal 3S, and primary winding 6 of track transformer 4TT, whereupon 20 code current of the second frequency is supplied at K to section KL. This current is ineffective to operate relay 5TB, which is tuned to respond to current of the first frequency, hence relays 5TR,'5D, 5H, 5FSA and 5138A are released. Signal 4S-accordingly is conditioned to display its stop aspect, and relay R becomes energized over a circuit extending from terminal B through back contact H of relay 5H, front contact 73 of relay 6H and the winding of relay 58R to terminal C. and relay 55R accordingly picks up to close its front stick contact 12. Front contact H of relay BSR also closes to tune relay 5TB to current of the second frequency, and relay ETR accordingly responds to the 20 code current in section K-L, and causes relays BFSA and BSA to pick up. In addition, contact 66 of relay 5SR is caused to operate from its back to its front position, to shift the current, supplied at L to section KL, from the second to the first frequency, as can readily be seen from an inspection of the drawings.

Relay BSPS picks up over an obviaus circuit including front contact 89 of relay ESR, to operate contact 90 from its back to its front position to shift the tuning of relay BTR from current of the second to the first frequency, and contact 5'6 of relay ESPS operates from its back to its front position to shift the current supplied at L to section LM from the first to the second frequency, whereupon section LM is supplied at L with current of the second frequency coded at the 20 code rate, over a circuit including secondary winding Id of frequency changer FC and primary Winding 6 of track transformer @T'I, back contact 4 associated with signal 48, back contact 80 of relay 68R, contact 20a of coder QCT and front contact 55 of relay SSPS. Relay ITR is nonresponsive to current of the second frequency, hence relays TTR, 1H, IFSA and TBSA drop. Relay 8SR accordingly becomes energized over a circuit including back contact H of relay 1H, front contact 13 of relay 8H, and the winding of relay SSR. Relay 8SR picks up to close its front stick contact 12, and operates its contact 92 from its back to its front position to tune relay lTR to current of the second frequency, whereupon relay 'ITR responds to the 20 code current in section LM with the result that relays IFSA and BSA pick up. Relay BSR also operates its contact 63 from its back to its front position so that current of the first frequency is supplied at M to section L-M over a circuit including back contact 4 associated with signal (is, contact 15 of coder ECT, front contact 65 of relay 8BSA, back contact 64 of relay ZLHSR, front contact 63 of relay 8SR and the secondary winding of transformer LTS.

It is, of course, apparent that with relay 'ITR tuned to current of the second frequency, relay TTR functions to repeat the code current from section LM into section MN, and at this time it is to be noted that section MN is supplied at M with current of the first frequency to which relay QTR is responsive. Relay STR, in following the 20 code current of the first frequency, causes relays 9H and 9D to be released. Relay 8TR responds at this time to current of the second frequency supplied at the opposite end N of the section.

From the foregoing description, it is readily apparent that when relay IRHSR is energized, signal is is cleared; the opposing signal as is conditioned to display its stop aspect; the ap paratus associated with the opposing signals is and BS is conditioned to prevent clearing of those signals (due to the releasing of relays 9H and 9D) should relay ZLI-ISR be energized; the frequencies of the track circuit currents supplied to the sections up to th siding section in advance are so controlled that current of traincontrol frequency is applied to the sections in the direction to be fed toward an eastbound train; and the track relays of such sections are tuned to respond selectively to current of the frequency applied at the opposite end of the associated section.

Signal 68 may be cleared by energizing relay ZRHSR, whereupon front contact 49 closes to complete the energizing circuit of signal 65 and that signal is conditioned to display its caution indication since relay 8D is released when relay 8TR operates in response to '75 code current repeated by relay IOTR into section MN. Contact 4 operated by signal GS accordingly is caused to assume its front position, whereupon the current supplied at M to section LM is shifted from the to the 180 code rate. Relay 6TB follows this 180 code current and picks up contact 60 to cause signal 58 to display its clear aspect.

The energization of relay 2RHSR also causes its front contacts 82 and 83 to operate from their back to their front positions, and as a result relay 8TR is tuned to respond to current of the first frequency while relay 9TR is tuned to respond to current of the second frequency. Contact of relay ZRHSR operates from its back to its front position to shift the current supplied at M to section MN from the first frequency to the second; contact 60 of relay 2RHSR operates from its back to its front position to shift th current supplied at N to section lVi-N from the second to the first frequency; back contact 96 of relay 2RHSR opens; and front contact 86 of relay 2RHSR closes to energize repeater relay ZRPSR. Contact I23 of relay ZRPSR accordingly operates from its back to its front position to tune relay lilTR tocurrent of the first frequency; and front contact 8? of relay ZRPSR closes to complete a circuit, comprising winding it of frequency changer F0, condenser l6, front contact 81 of relay ZRPSR, contact 2% of coder QCT, back contact 4 operated by signal ES, and the primary winding of transformer lEiTT; with the result that 20 code current of the second frequency is supplied at N- to th section to the left of section MN. This 20 code current, as pointed out hereinbefore, is effective to cause apparatus (not shown) at the opposite end of the section to cause current-of the first frequency, effective to operate relay WTR, to be supplied to the section. Relay lElTR accordingly responds to such current, which will be assumed to be coded at its normal or 75 code rate.

It follows, therefore, that with relays IRHSR and ZRHSR caused to be energized over the communication system, the apparatus represented in Fig. l is conditioned for an eastbound train movement and is arranged to supply track circuit current to each section so as to be transmitted through the track rails toward an eastbound train, thereby rendering possible the control of train-carried apparatus on the train.

If, now, an eastbound train enters the section to the left of section J-K, relay iTR is shunted and relays IFSA and IBSA release. Relay IBSA closes its back contact 10 to complete an obvious energizing circuit for the lamps of signals GS and 2S, with the result that signal is becomes effective to display an illuminated clear indication. When the train accepts signal IS and enters section JK, both relays 2TB. and 3TB are shunted, and relays ZFSA, ZBSA, 2H, 2D, SFSA and 338A release. Signal IS accordingly is caused to display its stop aspect, and contact s associated therewith is operated to its back position to complete a circuit path, including contact 28 of coder [CT and back contact fa l of relay ZBSA, over which 20 code current of the first frequency is supplied at J to the section to the left of section J-K after the train vacates the section.

When the train enters section KL, relays 4TR and 5TB are shunted, relays iBSA and SBSA are released, and contact 70 of relay EBSA closes to complete an obvious energizing circuit for the lamp SL of signal S, whereupon the signal is caused to display its illuminated clear aspect.

Relay 3TR is caused to operate at the 20 code rate, after the train vacates the associated section J-K, due to current supplied at J to the section, and relay 3BSA picks up. In addition, relay ZTR also is caused to operate at the 20 code rate by virtue of current supplied at K to section J-K over a circuit path including contact 20a of coder 3CT and back contact 6| of relay 4H. Relay ZBSA accordingly is caused to close its front contact 54 and complete an easily traced circuit over which '75 code current is supplied at J to the section to the left of section J-K.

When the train passes signal 5S and enters section LM, relays BTR and ITR are shunted. Relays EFSA, BBSA, 6H and 6D release to cause signal 58 to display its stop aspect, and contact 4 is operated by signal 53 into its back position to establish a circuit, including contact of coder 4CT and front contact 12! of relay ESR, over which 75 code current is supplied to section KL at L. This '75 code current causes operation of relay ATR when the train vacates the section, and relay 4H is picked up to condition relay ATR to repeat the '75 code energy into section JK, where it causes operation of relay ZTR and causes relay 2H to be picked up to condition signal IS to display its approach indication and operate its contact 4 to its front position to shift the coding of current, supplied at J to the section to the left of section J-K, to the 180 code rate. Relay 5TR also is caused to operate, when section KL is vacated, at the code rate and relays SFSA and BBSA are picked up, the latter relay opening the energizing circuit for the lamp of signal 58.

When the train enters section MN, relays 8TR and 9TB are shunted, the decoding relays associated with relay 8TB are released, and signal BS is caused to display its stop aspect. Relay IOTR is likewise shunted when the train enters the section to the right of section MN. After section LM becomes vacated, 20 code current is supplied at M to section LM over a circuit comprising the secondary winding of transformer LTS, condenser 9, front contact 63 of relay 8SR, back contact 64 of relay ZLHSR, back contact 65 of relay SBSA, contact 20 of coder 5CT, back contact 4 operated by signal 68 and the primary winding of transformer 'ITT. This 20 code current causes operation of relay BTR and causes relays SFSA and BBSA to pick up, but does not alter the condition of signal 5S. Relay ITR also operates at the 20 code rate when section LM becomes vacated, and relays IFSA and BSA are picked up.

After the train vacates section MN, relay 8TR operates at the 20 code rate, due to current supplied at N over a circuit path including back contact 6! of relay IOH and contact 20 of coder SGT, and relays 8FSA and 838A and accordingly are picked up. Front contact 65 of relay BBSA closes to supply '75 code current at M to section LM, over an easily traced circuit, and relay BTR in response thereto picks up relay 6H to condition signal 58 to display its caution indication. Contact l is operated by signal 58 into its front position, thereupon shifting the current supplied at L to section K-L to the 180 code rate. This 180 code current is repeated by relay 4TB. into section J-K where it causes operation of relay ZTR with the result that relay 2D is picked up, and signal IS is conditioned to display its clear indication.

Relay STR is caused to operate at the 20 code rate when section MN becomes vacated, relays QFSA and QBSA are picked up, and 20 code current is supplied at N to the section to the right of section MN.

Relay [OT-R is caused to operate at the code rate'in response to current supplied to the section in a manner, not shown but substantially corresponding to the manner described hereinbefore whereby '75 code current is caused to be supplied to the section to the left of section J-K after the passage of the eastbound train, and when this happens. relay NEH is picked up and relay IOTR repeats the 75 code into section MN. Relay BTR thereupon operates at the 75 code rate, and relay 81-1 is picked up to condition signal (is to display its caution aspect. Contact 4 of signal 63 operates to its front position to shift the coding of current supplied at M to section LM to the 180 code rate, whereupon relay BTR operates to pick up relay 6D and condition signal 58 to display its clear aspect. It follows, therefore, that the apparatus of Fig. 1 is restored to the condition hereinbefore described wherein it is arranged for an eastbound train movement.

t is apparent from the foregoing that the apparatus of Fig. 1 is organized so that when the communication system is suitably controlled for an eastbound train movement, the movement of an eastbound train through the stretch causes the eastbound signals in the rear to be successively cleared as the train proceeds through the stretch. This control of the signals is established without the use of line wires solely through the medium of track circuit current of the traincontrol frequency, hence it provides means for controlling either or both wayside signals and train-carried signals to permit following eastbound trains to move under signal indications governed by trafiic conditions in advance.

The apparatus of Fig. 1 may be restored to its normal condition, as represented in the drawings, by the operator suitably controlling the communication system to cause relays IRHSR and ZRHSR to be released, and by causing relay I SR to be released and relay ITR to be tuned to current of the first frequency. When relay ZRHSR releases, front contact 50 opens to deenergize signal 63 and cause that signal to be conditioned to display its stop aspect, whereupon contact 4 associated therewith operates to its back position to cause the current, supplied at M to section LM, to be coded at the 75 code rate. This 75 code current causes operation of relay 6TB, and relay 6D is released to cause signal 58 to be conditioned to display its normal caution aspect. The releasing of relay ZRHSR also causes its back contact 82 to close to tune relay STR to current of the second frequency; back contact 83 to close to tune relay 9TR to current of the first frequency; back contact 95 to close to shift current supplied at M to section MN to current of the first frequency; back contact 50 to close to shift the current, supplied at N to section MN, to current of the second frequency; front contact to open to deenergize repeater relay ERPSR; and back contact 96 to close. During the slow release interval of relay ZRPSR, current of the. second frequency, coded at the 75 code rate, is supplied at N to the section to the right of section M-N, over a circuit comprising winding M of frequency changer FC, condenser in, back contact 96 of relay ZRHSR, front contact 53 of relay 2RPSR, switch controlled contact 22-30, front contact 54 of relay ilBSA, contact 15 of coder 9CT, back contact 4 operated by signal IS and the primary winding of track transformer IOTT. This 75 code current of the second frequency is effective to cause the apparatus at the opposite end of the section to supply current of second frequency to the section, to operate relay HJTR. The manner in which this is effected will be understood best by considering the apparatus represented in Fig. 1A, which apparatus substantially corresponds to that provided at the opposite end (not shown) of the section to the right of section MN. Referring to Fig. 1A, when 75 code energy of the second frequency is made available in the section to the left of section J-K, relay ITR is caused to operate, and relays IFSA, IBSA and IH are picked up. Relay ISR accordingly is released, and its back contact 92 closes to tune relay ITR to current of the first frequency, and back contact I20 also closes to shift the current, supplied at J to the section to the left of section JK, to the second frequency. The slow releasing characteristics of relay ZRPSR are selected so that this relay releases at substantially the same instant that the stick relay at the opposite end of the section releases. When relay ZRPSR releases, its back contact I28 closes to tune relay IIJTR to current of the second frequency, and contact 53 operates from its front to its back position to shift the current, supplied at N to the section to the right of section M-N, from the second to the first frequency. It is apparent, therefore, that the track circuit apparatus of the section to the right of section M-N (which corresponds to that of the corresponding section to the left of section J-K) is restored to its normal condition wherein current of the first frequency coded at the 75 code rate is supplied to the rails for transmission in the westbound direction and current of the second frequency is supplied to the rails for transmission in the eastbound direction.

When relay IRHSR is caused to release, front contact 3! opens to deenergize signal i and condition it to display its stop indication and operate its contact 4 to its back position to shift the current, supplied at J to the section to the right of section JK, to the '75 code rate. In addition, relay IRHSR closes its back contact 82 to tune relay 2TR to current of the second frequency; back contact 83 closes to tune relay 3TR to current of the first frequency; back contact 96 closes to shift the current, supplied at J to section J-K, to the first frequency; back contact 50 closes to shift the current, supplied at K to section JK, to the second frequency; front contact 86 opens to deenergize repeater relay IRHSR; and back contact 85 closes. During the slow release interval of relay lRPSR, current of the second frequency coded at the '75 code rate is supplied at K to section KL, over a circuit comprising winding I4 of frequency changer FC, condenser l0, back contact 85 of relay IRHSR, front contact 53 of relay IRPSR, front contact 54 of relay SBSA, contact of coder 3CT, back contact 4 operated by signal 35, and the primary winding of transformer 4'I'I'. This '75 code current causes operation of relay 5TR, and relay 5H is picked up to cause relay 58R to release. When this happens, back contact H closes to tune relay 5TR to current of the first frequency, back contact IZI of relay 58R closes to shift the current supplied at L to section K-L to the second frequency, and front contact 89 of relay 5SR opens to deenergize repeater relay ESPS. The slow acting characteristics of relay IRPSR are selected so that this relay releases at substantially the same time that relay 53R releases. When relay IRPSR releases, relay 4TB. is tuned to current of the second frequency, current of the first frequency is supplied over back contact 53 of relay IRPSR, to section LM, and the track circuit apparatus of section LM is restored to its normal condition wherein current of the first frequency is caused to operate relay ETR and current of the second frequency is caused to operate relay 4TB.

This current of the first frequency, operating relay 5TB, is coded at the normal rate of 75 cycles per minute, hence signal 48 is conditioned to display its approach aspect and contact 4 is in its front position. At this time, during the slow release interval of relay 5SPS, current of the second frequency coded at the code rate is supplied at L to section LM, over a circuit comprising winding [4 of frequency changer FC, condenser lll, front contact 56 of relay 5SPS, contact i8lla of coder 4CT, front contact 4 operated by signal 4S, and the primary winding of transformer GTT. Relay 'ITR accordingly is caused to operate at the 180 code rate, and picks up relays 'ZFSA, TBSA and Ill. The 180 code current is repeated by relay ITR into section MN where it causes operation of relay QTR to pick up relays 9I-I and 9D.

Relay BSR also is caused to release when relay 1H picks up, and relay BSR closes its back contacts 92 and 63 to shift, respectively, the tuning of relay 'ITR to current of the first frequency, and the current supplied at M to section M-N to the second frequency. The slow releasing characteristics of relay ESPS are selected so as to permit relay 5SPS to release at substantially the same instant that relay 8SR releases. When relay 5SPS releases, relay BTR is tuned to current of the second frequency, current of the first frequency is supplied at L to section LM, and the track circuit apparatus of section LM is restored to its normal condition wherein relay 'ITR follows 1.80 code current of first frequency and relay iiTR follows 7 5 code current of the secfrequency. The apparatus of Fig. 1 accordingly is restored to its normal condition, as represented in the drawings.

From the foregoing, it is readily apparent that the apparatus of Fig. l is arranged so as to be conditioned from a remote point for either an eastbound or a westbound traffic movement, and when so conditioned the apparatus is arranged so as to effect the control of either or both wayside signals and train-carried cab signals by means operated, without the use of control line wires, solely through current transmitted through the track rails.

A modified arrangement of the apparatus of 1 is represented in Fig. wherein apparatus embodying my invention is arranged to control only wayside signals and not cab signals, hence no provision is made for governing the frequencies of current fed to the rails of a section so as always to supply the current for transmission through the rails toward a train on the stretch.

Referring now to Figs. 2A to 2D, inclusive, the track relays TR connected to the right-hand ends of the track sections and having odd numbers as prefixes are represented as being constantly tuned by condensers 9 to current of the first frequency while the other relays connected at the opposite or left-hand ends are represented as being constantly tuned by condensers l!) to current of the second frequency. Each relay TR, represented in Fig. 2 is energized by current of the proper frequency suppliedat the opposite end ofthe section, and such current is normally coded at the relatively low code rate of, say 20' code cycles per minute. This coding of the current, as pointed out hereinbefore, is ineffective to cause the track relays TR. to pick up the associated H and D decoding relays, but the associated FSA and BSA relays are picked up. With all signal control decoding relays H and D released, and the remotely controlled signal control relays lRHSR, l-LHSR, ZRHSR and ZLHSR released, all signals are conditioned to d splay their respect ve stop aspects.

In addition to the previously mentioned remotely controlled switch and signal control relays of Fig. 1, the apparatus of Fig. 2 is arranged to provide each station at the ends of the stretch, with two other remotely controlled relays, one relay USR of which is provided for locally conditioning an associated signal to display its stop indication. Relay USR, at the right-hand end of the stretch, for example, when energized opens back contact mu interposed in the easily traced control circuit of signals 18 and 88, with the result that if signal is is conditioned to be cleared by the energization of either or both of the associated signal control decoding relays 9H and 9D, the energization of relay USR removes relays 9H and 9D from control of such signal and the signal accordingly is set to stop. The other remotely controlled relay BS at that end of the stretch is provided for clearing locally signal BS2, as is customary in remote control of signals. For example, when section MN is unoccupied so that relay SBSA is energized to close its front contact lfll and switch WI is reversed so that contact 28 operated by the switch mechanism is in engagement with contact 34, the energization of relay BS and consequent closing of its front contact H34 completes an easily traced circuit for signal whereupon that signal is cleared.

In the normal condition of the apparatus of Fig. 2, as represented in the drawings, it is assumed that the section to the right of section MN is supplied with current of the second frequency coded at the 20 code rate to cause relay IDTR to operate at such code rate and pick up relays lOFSA and IBBSA, while current of the first frequency coded at the 20 code rate is supplied to the section to the left of section JK and causes relay ITR to respond and pick up relays IFSA and IBSA. With the two end sections supplied with current of 20 code, and all remotely controlled signal and switch control relays released, as shown, sections JK, K-L, LM and MN are supplied at their respective left-hand ends with 20 code current of the first frequency. For example, with relay IH released, 20 code current of the first frequency is supplied to section JK at J over a circuit including the secondary winding of'line transformer L-Tl, back contact of relay IH, contact a of coder ICT and the primary winding of track transformer ZTT. These sections are likewise supplied at their opposite or right-hand ends with 20 code current of the second frequency, as is readily apparent from an inspection of" the drawings; All

. quency is supplied at M to section LM over an easily traced circuit including secondary winding 14 of frequency changer FC, front contact 106 of relay ZRHSR, front contact ID? of relay BBSA, contact 15 of coder 101, back contact 4 associated with signal 6S and the primary winding of track transformer 'ITT. Relay ETR follows this code current and relay SE is picked up to condition signal 58 to display its caution aspect. Relay ESR also picks up over an obvious circuit including front contact H18 of relay 6H, and front contact I I5 of relay 68R closes to complete an obvious stick circuit through back contact i 58 of relay 5H. Current of the second frequency coded at the 180 code rate is now supplied to section KL over a circuit including primary winding l4 of frequency changer FC, front contact I 09 of relay 68R, contact I of coder ECT, front contact 4 associated with signal 58 and the primary winding of track transformer 5TT. Relay 6TB responds to this code current and picks up relay 4H. With relay 4H picked up, relay GTE functions to repeat into section JK the 180 code current, over a circuit comprising winding M of frequency changer FC, back contact ll! of relay IUSR, front contact H2 of relay 4H, contact 52 (when closed) of relay dTR, and the primary winding of track transformer 3TT, thereby causing relay 2TR to operate and pick up relays 2H and 2D. Signal is accordingly is cleared when relays 2H and 2D pick up, and it follows that when relay ZRHSR at one end of the stretch is energized, signal IS at the opposite end is cleared by means of control energy which is transmitted from one end to the other of the stretch wholly through the rails of the stretch. When signal I S clears, contact 4 associated therewith operates to its front position to condition the apparatus to permit the signal at the other end (not shown) of siding track Y to be cleared. That is to say, if signal IS is cleared and the operator selects relay IRHSR for operation by the communication system and causes that relay to pick up and close its front contact H9, 180 code current of the second frequency is supplied to the section to the rear of section JK over a circuit including secondary winding M of frequency changer FCI front contact Ht of relay IRHSR, front contact ill! of relay ZBSA, contact I80 of coder lCT, front contact 4 associated with signal IS, and the primary winding of track transformer ITT. While the intermediate portion and opposite end of siding track Y are not shown, the siding ordinarily will be provided with apparatus substantially corresponding to the apparatus shown in'Figs. 2D'and and 2C, corresponding to the intermediate portion and the left-hand end of siding track Z, respectively. The complete siding Y may, therefore, be illustrated by placing Figs. 20, 2D'and 2A together in the order named with Fig. 20 on theleft, and it follows that if signal IS is cleared and relay IRHSR is picked up, the 180 code current supplied to the section in the rear of section JK is effective to operate the track relay (which may correspond torelay 8TB, o1" Fig. 2C) 

